Process for making coating materials for deoxidation of rust



Patented Jan. 10, 1933 UNITED STATES BUDOLI EBEBHABD, OF MUNICH, GERMANYIPBOCESS FOR MAKING COATING MATERIALS FOB DEOXIDATION OF BUST HoDrawing. Application filed Kay 5, 1927, Serial No. 189,184, and inGermany March 29, 1826.

This invention relates to a process for removing and preventing theformation of rust on iron, a composition of matter to be used for thispurpose and a process for making such a composition. Hitherto it hasbeen customary to remove rust by dissolving it in acids thereby leavinga fresh clean surface of iron exposed. This method is objectionablesince the body of iron is gradually destroyed. Moreover, the fresh ironsurface is not only susceptible to further rusting, but such rusting isactually promoted by acid which cannot be entirely removed from thepores of the iron.

It is true, methods are already known for deoxidation of the rust, butwith them it is, on principle, a matter of exposing the rusted ironparts in baths to the action of hydrogen.

, For coating materials such methods are not applicable; besides they donot produce a 1 rust protecting effect at the same time.

According to the present invention, however, compounds are applied tothe surface of the iron which react with the iron rust and bydeoxidation convert it into magneticoxide of iron (Fe O The reducedmetal compounds which are formed remain in solution and in this solutionexert the deoxidizing action on the rust. In consequence of theevaporation of the solvent or vehicle, the metal compounds graduallyprecipitate onto the magnetic oxide of iron and form with the lattercorresponding complex compounds,

thus forming a protective layer or coating on the iron.

With the present process such metal compounds are employed in theirreduced state and dissolved in reducing organic solvents without a fatoroil-character, which, in consequence of their tendency to oxidizethemselves deprive the rust of a part ofv its oxygen, reducing it tomagnetic oxide and being themselves oxidized thereby and also by takingup some oxygen from the air to oxidized substances which are chemicallyindifierent to substances promoting the formation of rust.

By the expression reduced state is meant that the metal compounds usedcontain the metal at a valency which is lower than the highest valencyof that metal; for example, in the compound used the valency of themetal may be 2 whereas the metal may also have a valency of 3 or more.In other words thetious compounds rather than the ic are use Thereduction of the metal compounds will be best accomplished by means ofuric acid alone or in combination with urea, dissolved in formaldehydeand that in the presence of metals such as zinc dust, copper, lead,aluminium, mercury as catalysts.

It has been found, that the dissolving of the uric acid in formaldehydetakes place easily in the presence of these catalysts and withoutheating the formaldehyde up to its boiling point, whilst in theirabsence the uric acid goes only poorly and but partly into solutionafter a prolonged heating up to the boiling point.

In place of formaldehyde or together with the same its polymerizationorcondensation products as well as compounds splitting ofi formaldehydemay be used as reducing organic solvents for the uric acid or for themetal compounds reduced by it respectively.

The compounds of chromium, molybdenum, tungsten and lead, soluble in theaforementioned solvents and reducible in the corresponding manner havebeen found. among others, to be particularly suitable. For theattainment of complex reducible metal compounds the above mentionedmetal compositions may be combined with suitable compounds of antimony-,manganeseor zinc compounds.

For example, by the. present process 5 parts by weight of uric acid aremixed with 50 parts by weight of formaldehyde and 0.5 parts by weight ofzinc dust are added. On shaking, the mixture is then heated up to 60-7 0C. A yellowish clear liquid results, that may be marked: Originalsolution in the following examples. The liquid is decanted from thesettled zinc. The composition may be prepared by the use of the originalsolution as such or the uric acid may be mixed with the reducible metalcompound and any other ingredients desired to be 0.5 parts by weight ofcaustic incorporated and the mixture dissolved in the aldehyde organicsolvent.

Example 1 0.8 arts b wei ht of tun stic anh dride, p y g g otash (1': 2)and 0.5 parts by weight of phosphoric molybdic acid are dissolved in 40parts by weight of original solution. A dark green liquid is obtained,containing the metal compounds in the reduced'state which is indicatedby the color of the solution.

Example 2 0.8 parts by weight of tungstic anhydride, 1 part by weight ofcaustic potash (1:2) and 0.4 parts by weight of uric acid are wellground together and then mixed and well ground with 1 part by weight oforthophosphoricacid (1,7 specific gravity). Then are added 40 parts byweight of formaldehyde and 0.1 art by weight of zinc dust. The whole iseated up to 75 C., a blue solution resulting.

' Example 8 1 part by weight of tungsten trioxide, 0.5 parts by weightof caustic potash (1: 2), 0.4

parts by weight of uric acid and 10 parts by weight of paraformaldehydeare ground together, until the mixture has assumed a een color. Then themixture is dissolved in parts by weight of water through boiling withthe addition of a small portion of zinc dust. A blue solution will bethe result.

Further experiments have shown, that greater amounts of reduced metalcompounds will dissolve in the original solution or in formaldehyderespectively, if urea will be added to the uric acid or to theformaldehyde or to both of them. It was further found out, thatespecially with the use of metal salts or metallic oxides the additionof acids will not only facilitate the reduction of the former throughuric acid, but also the dis solving in formaldehyde or in the originalsolution respectively. As acids, weakinorganic or organic acids may beused.

- Exwmple 4 2 weig t of phosp oric molybdic acid and 3 parts by weightof urea are well grounl together and then dissolved in parts by weightof formaldehyde.

Example 5 similar organic reducing agents soluble in formaldehyde may beadded to the uric acid or to the uric acid-formaldehyde solution.

Having now particularly described and ascertained the nature of thisinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

1. The process of deoxidizing rust and preventing further formation ofthe same which comprises coating a rusty surface with a solution of atungsten compound in a mixture of uric acid and formaldehyde.

2. The rocess of deoxidizin rust and reventin rther formation t ereof wich comprises coating a rusty surface with a solution of a compound of ametal selected from the class consisting of chromium, molybdenum,tungsten and antimony in a mixture of uric acid and formaldehyde.

3. The recess of deoxidizin rust and reventing urther formationcomprises coating a rusty surface with a solution of a compound oftungsten and molybdenum in a mixture of uric acid and formaldehyde.

4. The process of deoxidizing rust and reventingrther formation thereofw ich comprises coating a rusty surface with asolution of a compound oftungsten, molybdenum and chromium in a mixture of uric acid andformaldehyde.

In testimony whereof I hereunto aflix my signature.

' RUDOLF EBERHARD.

arts by wei ht of uric acid, 3 parts by ereof w 'ch'

